Things that aren't tested can pretty much be counted on to fail a non-trivial percentage of the time. If it's going to be business critical, then it needs to be tested. (Lesson hopefully learned here)

By the same token, things which aren't monitored can also be counted upon to fail a non-trivial percentage of the time and even worse, go unnoticed. (Another teachable point here)

...but people being what they are tend to learn these things the hard way unless we've got concrete, real-world incidents like this for them to learn from.